A Delhi Police team investigating the mysterious death of Congress leader Shashi Tharoor’s wife Sunanda Pushkar, is likely to visit the US by the month end to bring back her viscera samples lying with the FBI for nearly an year.

Police sources said the step was being taken following a Ministry of Home Affairs letter reminding it to get the samples back as was asked by the FBI lab since samples were lying there despite a report by the US agency lab.

51-year-old Sunanda was found dead at a suite in a five-star hotel in South Delhi on the night of 17 January, 2014, a day after her spat with Pakistani journalist Mehr Tarar on Twitter over her alleged affair with Tharoor, the Congress MP from Thiruvananthapuram in Kerala. In January 2015, Delhi Police had registered a case of murder in connection with the death of Sunanda.

An AIIMS medical board had earlier found poisoning as reason for her death following which the police had sent her viscera samples to an FBI lab in US. The FBI lab report, sent to Delhi Police in November 2015, endorsed the findings of the AIIMS forensic report. As police could not firm up about cause of the death based on the FBI report, they requested a medical board of AIIMS to analyse the contents of the report.

During the investigation, several persons including Shashi Tharoor have been questioned in connection with Sunanda’s death. The police have also conducted polygraph test on six persons, all prime witnesses in the case, including Tharoor’s domestic help Narayan Singh, driver Bajrangi and Sanjay Dewan, a close friend of the couple.

In February this year, Tarar was questioned about her relation with the Congress leader and his wife, her fight with Sunanda over Twitter, and other issues revolving around Sunanda’s mysterious death.